1. Field of the Invention
This invention relates to capacitive discharge ignition systems in which a storage capacitor is charged by a generator or alternator and is discharged by a silicon-controlled rectifier (SCR) or thyristor switch triggered conducting in synchronism with the engine.
2. Description of Related Art
The Problem of turning SCRs off in capacitive discharge ignition systems is well known. Once triggered to conduct, the SCR remains conducting until the current source stops and the triggering pulse is removed. A number of patents have addressed shutting down the anode-to-cathode current from the source charging the storage capacitor. These have all related to direct current to direct current converter power supplies which can be electronically shut-down. See, for example, U.S. Pat. Nos. 3,583,378; 3,800,771; 3,838,328; and 4,069,801. The output of an alternator or generator cannot be switched off as with direct current converter power supplies. The output being an alternating current will periodically pass through zero. At this time, the SCR will shut down. However, it is desired to shut down the SCR immediately, that is, without waiting for the next polarity reversal of the alternator or generator. The applicant's circuit is directed to the shutting off of the power SCR in a capacitive discharge ignition system supplied by a generator or alternator.
U.S. Pat. No. 4,522,184 specifically addresses these shortcomings, but does so at the cost of added circuit complexity. The present invention reduces power loss and provides simplified circuitry.